bug#13580: 24.2.92; regression in calc-convert-units

[Glenn Morris]

Jay Belanger wrote:

>   * the difference between the old behavior and the pretest behavior is
>     that one bug was fixed, making it easier to see another bug which
>     had been around a while (the pretest buggy behavior wasn't new),
>   * the changes since the pretest have been simple, but not trivial,
> I'll leave the pretest alone.

Sounds like the right call to me.